Behavioural switching mechanism of crayfish avoidance reaction after establishment of social hierarchy

当螯虾呈静止姿态时，机械刺激尾扇引起回避反应，其反应模式根据螯虾的大小由投镖反应转变为转身反应。此外，当两个以前不认识的小龙虾遇到，战斗立即发生，并在几次接触中确定了主从关系。我已经表明，在这项研究中，小龙虾，以前显示飞镖反应响应机械刺激的尾扇改变了他们的表现回避反应时，他们赢得了与对手的战斗。虽然它们在战斗前主要表现出飞镖反应（约92%），但触摸尾扇主要引起转向反应（94%）。统计分析表明，打斗前后，优势种克氏原螯虾的飞镖反应和转身反应的发生概率差异极显著（p<0.0001：配对t检验）。战斗结束后， 关于我们 通常观察到纵列动物会逃离占优势的小龙虾的接近。从属的小龙虾对机械刺激的反应几乎是一致的。为了研究优势种克氏原螯虾回避反应的行为变化，连续测定了3个不同组别的克氏原螯虾对感觉刺激的反应。第1组中，将主、副螯虾继续配对8d。超过一半的下属在5天内被占优势的小龙虾杀死。当施加机械刺激时，显性持续偏好执行转向反应。第1天试验结束后，将第2组的优势个体与其下属个体重新隔离。随着时间的推移，转弯反应发生的概率降低，而飞镖反应发生的概率增加。在第2天和第3天，转身反应的发生概率仍显著高于飞镖反应。在第4天，转向反应和飞镖反应之间没有明显的偏好，从第5天开始飞镖反应的释放更频繁。第3组在试验结束后将主、从螯虾分开，但从第2天开始将两种螯虾配对1 h。在第8天，占优势的小龙虾继续表现出转向反应。这表明，与下属的接触是保持回避反应的行为转变所必需的。少

When the crayfish showed resting posture, mechanical stimulation to the tailfan elicited avoidance reaction in which response pattern was changed from dart to turn response according to the size of the crayfish. Furthermore, when two previously unacquainted crayfish encounter, fighting occurred immediately and dominant-subordinate relationship was determined within several contacts.I have shown in this study that small crayfish that previously showed dart response in response to mechanical stimulation to the tailfan changed their performance of avoidance reaction when they won the fights with opponents. While they mainly showed dart response (about 92% from 47 crayfish) before fighting, the touching tailfan predominantly elicited turn response (94%). Statistical analysis showed the occurrence probability of the dart response as well as that of the turn response was significantly different between dominant crayfish before and after fighting (p<0.0001: paired t test). After fighting, sub … More ordinate animals were usually observed to run away from the approach of dominant crayfish. The response of the subordinate crayfish to the mechanical stimulation was almost consistent. Touching of the exopodite mainly elicited dart response before (95% from 47 animals) and after (91%) fighting.To characterize behavioral change of the avoidance reaction in the dominant crayfish, the response of them to the sensory stimulation was continuously tested with 3 different groups. In the 1st group, the dominant and subordinate crayfish were kept to pair for further 8 days. More than half of the subordinates were killed by dominant crayfish within 5 days. Dominant continuously preferred to perform the turn response when the mechanical stimulation was applied. Dominant crayfish of the 2nd group were re-isolated from the subordinates immediately after the test of the 1st day. As days have passed, the probability of the occurrence of the turn response was decreased and that of dart response was increased. Occurrence probability of turn response was still statistically higher than that of dart response in the 2nd and 3rd day. There was no significant preference between turn and dart response in the 4th day, and the dart response was released more often from the 5th day. In the 3rd group, the dominant and subordinate crayfish were separated after the test but both crayfish were paired together for 1 hour from next day. The dominant, crayfish continue to show turn response even in the 8th day. These suggested contact with subordinate is needed to keep the behavioral transition of avoidance reaction. Less